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    Subject[patch 40/71] sched: fix nr_uninterruptible accounting of frozen tasks really
    2.6.30-stable review patch.  If anyone has any objections, please let us know.

    ------------------

    From: Thomas Gleixner <tglx@linutronix.de>

    commit 6301cb95c119ebf324bb96ee226fa9ddffad80a7 upstream.

    commit e3c8ca8336 (sched: do not count frozen tasks toward load) broke
    the nr_uninterruptible accounting on freeze/thaw. On freeze the task
    is excluded from accounting with a check for (task->flags &
    PF_FROZEN), but that flag is cleared before the task is thawed. So
    while we prevent that the task with state TASK_UNINTERRUPTIBLE
    is accounted to nr_uninterruptible on freeze we decrement
    nr_uninterruptible on thaw.

    Use a separate flag which is handled by the freezing task itself. Set
    it before calling the scheduler with TASK_UNINTERRUPTIBLE state and
    clear it after we return from frozen state.

    Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
    Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

    ---
    include/linux/sched.h | 3 ++-
    kernel/freezer.c | 7 +++++++
    2 files changed, 9 insertions(+), 1 deletion(-)

    --- a/include/linux/sched.h
    +++ b/include/linux/sched.h
    @@ -206,7 +206,7 @@ extern unsigned long long time_sync_thre
    ((task->state & (__TASK_STOPPED | __TASK_TRACED)) != 0)
    #define task_contributes_to_load(task) \
    ((task->state & TASK_UNINTERRUPTIBLE) != 0 && \
    - (task->flags & PF_FROZEN) == 0)
    + (task->flags & PF_FREEZING) == 0)

    #define __set_task_state(tsk, state_value) \
    do { (tsk)->state = (state_value); } while (0)
    @@ -1630,6 +1630,7 @@ extern cputime_t task_gtime(struct task_
    #define PF_MEMALLOC 0x00000800 /* Allocating memory */
    #define PF_FLUSHER 0x00001000 /* responsible for disk writeback */
    #define PF_USED_MATH 0x00002000 /* if unset the fpu must be initialized before use */
    +#define PF_FREEZING 0x00004000 /* freeze in progress. do not account to load */
    #define PF_NOFREEZE 0x00008000 /* this thread should not be frozen */
    #define PF_FROZEN 0x00010000 /* frozen for system suspend */
    #define PF_FSTRANS 0x00020000 /* inside a filesystem transaction */
    --- a/kernel/freezer.c
    +++ b/kernel/freezer.c
    @@ -44,12 +44,19 @@ void refrigerator(void)
    recalc_sigpending(); /* We sent fake signal, clean it up */
    spin_unlock_irq(&current->sighand->siglock);

    + /* prevent accounting of that task to load */
    + current->flags |= PF_FREEZING;
    +
    for (;;) {
    set_current_state(TASK_UNINTERRUPTIBLE);
    if (!frozen(current))
    break;
    schedule();
    }
    +
    + /* Remove the accounting blocker */
    + current->flags &= ~PF_FREEZING;
    +
    pr_debug("%s left refrigerator\n", current->comm);
    __set_current_state(save);
    }



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